Polypyrrole wrapped graphene/TiO2 composites hydrogels for high performance supercapacitors

The graphene-based composite hydrogels with three-dimensional networks are considered as one kind of the most unique electrode materials for supercapacitors. Herein, the hydrogels based on polypyrrole (PPy) wrapped graphene/TiO2 composite are synthesized by one-pot hydrothermal treatment and subsequent chemical polymerization of pyrrole. The PPy wrapped graphene/TiO2 composite hydrogel exhibits enhanced electrochemical capacitance due to the interconnected three-dimensional nanostructure, the synergistic effect of the pseudo-capacitance of PPy and TiO2 and the electric double layer capacitance of graphene. The bind-free composite hydrogel possesses an excellent specific capacitance of 300 F g(-1) at the current density of 0.5 Ag-1. In addition, the composite hydrogel shows a stable capacitance in long-term cycles and its specific capacitance retention is more than 90% after 3000 charge-discharge cycles. It is expected that the PPy wrapped graphene/TiO2 composite hydrogel can be directly used as an ideal electrode material for high-performance energy storage devices.